Magnetron electron discharge devices



July 24, 1962 Filed Sept. 10, 1959 P. P. DERBY ETAL MAGNETRON ELECTRON DISCHARGE DEVICES 2 Sheets-Sheet 1 /NVENTOR PALMER 1 DERBY LEONARD W GE/ER BY/VWM A TTORNE Y July 24, 1962 P. P. DERBY ETAL 3,046,445

MAGNETRON ELECTRON DISCHARGE DEVICES Filed Sept. 10, 1959 2 Sheets-Sheet 2 INVENTOP PAL/VIE P DERBY LEON/4RD WGE/ER ATTOii/Vf) 3,046,445 Patented July 24, 1962 3,046,445 MAGNETRON ELECTRON DISTIHARGE DEVICES Pairner P. Derby, Weston, and Leonard W. Geier, Natick, Mass, assignors to Raytheon Company, Waltham, Mass, a corporation ofDelaware Filed Sept. 10, 1959, Ser. No. 839,148 8 Claims. (Qt. 315-3951) This invention relates to electron discharge devices of the magnetron type. 1

One of the objects of the presentinvention is to provide a magnetron which may be fabricated readily and simply from subassemblies which can be assembled, inspected and stockepiled as independent units.

Another object of the invention is to provide a magnetron in which the assembly of units intoa completed tube assembly is accomplished by the use of allowable and proven methods of construction, thereby achieving considerably reduction in cost of assembly and materials and reducing the possibility of scrap and errors in manufacture.

' Other and further objects and advantages of the present invention will become apparent as the following description progresses, reference being had tov the drawing where- FIG. .1 is a pictorial view illustrating a complete magnetron package according to the invention;

FIG. 2 is an exploded view of a magnetron assembly according to the invention, with the various subassemblies partly broken away to illustrateinternal details;

FIG. 3 is a view showing an input lead-in assembly for receiving cathode and heater leads;

FIG. 4 is a view showing the manner of joining the anode subassembly to the header subassembly prior to seal-in; and

FIG. 5 is a View showing the complete magnetron tube assembly minus the magnet assembly and output transmissionli'ne.

Referring to the drawings, the numeral 13 (shown in FIG. 1) generally designates a complete magnetron package includingan electron discharge tube 12 of the magnetron type, an accompanying magnet assembly 14, an output transmission line 75, and accessories, to be described later, for clamping the tube 12 in the fixed position with respect to the magnet assembly and to the transmission line. The magnetron tube assembly 12 includes a centrally disposed cathode-heater subassernbly 16 and a surrounding anode assembly 18. An electric field is created between the anode and cathode, in the usual manner, while a magnetic field transverse to the electric field is produced by the magnet assembly 14, shown in FIG. 1. The magnetron tube assembly 12 further comprises a header subassembly Ztl, a shell-'subassembly 22, and an input lead-in subassembly 21 secured to the header subassembly and sometimes referred to as a part of the header subassembly.

The anode assembly 18 includes an anode block 24 containing a cylindrical opening 25 from whose inner periphery radially extend several anode vanes 27, either integral with the anode block or secured thereto, as by soldering. The space between each pair of adjacent anode vanes at least partially defines a cavity resonator, as is well under stood in the magnetron art. Although the anode shown is of the vane type, the invention is not limited thereto; for example, the anode may be of the hole-and-slot type,

. resonant .anode structure.

assembly 25:. A circular slot is provided along the opposite edge 51 of the anode block 24 for receiving a ring 33. A lead 34, one end of which is attached to one of the anode vanes 27, serves as an output coupling lead for the magne ton, and, together withthe ring 33, formsa short coaxial line section. This output lead 34 preferably is crirnped, as shown in. FIGS. 2 and 4, to provide an effective coupling loop for coupling energy out of the magnetron cavity resonator system. i The cathode-heater subassembly 16 comprises a cathode cylinder 36 which maybe surrounded at the central-portion thereof by a wiremesh 37 containing an electronemissivematerial. The wire mesh may have metal powder brushed into it and may be sintered to the cathode cylinder. Annular end "shields38 of diameter somewhat in excess ofthat of the cathodezcylinder 36 are provided at eachend of the cathodec-ylinder tominimizct-formation of deposits of emitting material on other parts ofthe magnetron owing to .endwise emission from the cathode. A heater coil 49 is disposed within the cathode cylinder 36 andpnerend ofthis heatercoil is attached to the inner periphery of the cathode cylinder adjacent one end thereof. Themagnetron header subassernbly 20,includes a more or less cup-shaped member 42 of Csheet material provided with a central aperture forreceiving a portion of the leadin.-subassembly 21. The cupshaped member- 42, which maybe m-ade. of a copper-nickel alloy, includes a base portion 43 which is substantially flat; this base portion is bent .over along the periphery to provide a lip or rim portion 44. The lead-in.subassembly 21, shown in FIGS. 2 and 4, includes a metal input sleeve 45 to one end of which a glass or ceramic seal 46 is bonded for supporting a heater lead-in conductor 47 and a. cathode lead-in conductor 48 in spaced relation with respect to one another and to the metal sleeve 45. Conventional glass-toanetal sealing techniques may be ,used in forming, the lead-in assembly 21 The cylindrical sleeve 45 is inserted in the central aperture of the header subassernbly Ziland brazed to or otherwise secured thereto; The input sleeve 45 is made of a material having a thermal coefficient of expansion approximating that of the vitreous sealing material so that a good vacuum-tight bond is provided inthe region of the" seal; this is particularly important {when the header subassembly is made of a copper-nickel alloy or other material to which a vitreous material does not readily bond.

7 Alternately, the central aperture in'the base portion 43 of the header member 42 could be-upset to 'forma'n an-j nular shoulder 45 to which the glass seal; 46 is bonded,

bl'ock24: The anodebl'ock is providedflwith "an arcu ate slot to accommodate the ring. The ring serves efiectively as an outer conductor of an output coaxial line with the anode output lead 34 serving as the inner conductor. The anode block is mounted on the base portion 43 of the header member 42, as shown in FIG. 2, and the legs 28 are spot-welded to the base portion 43. The legs 28 facilitate spot-welding of the anode block 24 to the base portion 43 of header member 42 and provide a current path between welding electrodes positioned along edge 51 of the anode block and the underside of the header member 42. If the anode block 24 and the header subassembly both are made of a copper-nickel alloy, an excellent bond between the anode subassembly 18 and the header subassembly 20 is achieved. The anode subassembly 18 is positioned accurately on the header member 42 prior to spot-welding by an appropriate jig which insures that the anode block 24 is properly located with respect to the periphery of the member 42. This desired location normally occurs when the edge 52 of the anode block 24 and the edge opposite thereto are equidistant from the edge of the base portion 43 and when the end face 54 of the anode block 24 and the face opposed thereto are equidistant from the rim of header member 42.

The cathode-heater subassembly 16, with one end of the heater attached to the inner periphery of the cathode cylinder 36, is inserted in the space between the vane tips of the anode block 24. While the cathode is maintained centered in the anode space by an appropriate jig, the free end of the heater 40 is spot-welded to heater lead-in conductor 47 and the cathode lead-in conductor 48 is spot-welded to the cathode cylinder 36. The cathode and heater lead-in conductors each are bent, if necessary, to a position such that the conductors pass over the magnetron anode block 24 along the edge of an anode vane. disposed in juxtaposition with the edge of a first anode vane, while the heater lead-in conductor is radially disposed in juxtaposition with the edge of a second anode vane along which an RF. current flows in the same phase as the RF. current flowing in said first vane. With this arrangement, the R.F. magnetic fields linking the lead-in conductors are in the same direction in both conductors and the current induced in the cathode and heater lead-in conductors is in the same direction in both conductors. Consequently, the net RF. current induced in the heater-cathode circuit is a minimum. This position, then, is the position of minimum RB pickup by the cathode and heater leads. The heater conductor 47 is crimped to allow it to occupy the desired position for minimum R.F. energy pickup. A clamp 56 surrounding the cathode lead-in conductor 48 is secured, as by welding, to the face 54 of anode block 24 to lend support to the cathode lead-in conductor 48 and, hence, to the cathode-heater subassembly. A ferrule 57 made of an electrically insulating material, such as ceramic, surrounds the cathode lead-in 48 and is disposed within the clamp 56; this ferrule serves to insulate the cathode from the anode. An additional clamp may be provided, if necessary, around the heater lead-in conductor.

In fabricating the magnetron tube assembly 12, the lead-in conductors 47 and 48, which are flexible wires of relatively small gage, are first sealed into input sleeve by means of a glass head 46. The sleeve 45 is made of a material which will bond readily with glass. The

sleeve 45, with the conductors 47 and 48 in place, next is brazed into the center hole of header member 42 of the header subassembly 20 at the same time that the exhaust tube 49 is brazed to the header member 42. In the arrangement shown in FIG. 3, of course, it is necessary only to glass-in the leads 47' and 48 to the extension 45' of the header member 42. In FIG. 3, the heater lead-in conductor of lead-in assembly 21 is shown as composed of two separate wires 47' and 47", while the cathode lead-in conductor is shown as constituting two wires 48' and 48". The portions 47' and 48 are The cathode lead-in conductor is radially made of a material having a thermal coefiicient of expansion substantially equal to that of the glass bead 46, while the portions 47" and 48 are made of a refractory material, such as tantalum, which is capable of operating at high temperatures. The compound leads shown in FIG. 3, of course, may be used in the device shown in FIGS. 2 and 4, while the leads shown in FIGS. 2 and 4 may be used in the input lead-in assembly 21 of FIG. 3. The sealed-in heater and cathode lead-in conductors 47 and 48 are bent slightly until they are in line and so that they will not interfere with either the anode subassembly 18 which is to be bonded to the portion 43 of header member 42, or with the enclosure portion 63 of the shell subassembly 22 which, as will be seen subsequently, fits over the anode block 24 and the lead-in conductors. This alignment of the lead-in conductors may be done visually with sufficient accuracy.

The shell subassembly 22 may be stamped out of sheet metal and comprises a cup-shaped element 60 including a fiat circular base portion 61 bent over at the edges to form a lip or rim 62 and an enclosure portion 63 of substantially rectangular cross section extending from the flat portion. The enclosure portion 63 is adapted to fit over and enclose the anode subassembly 18, as well as the heater and cathode lead-in conductors. The shell subassembly may be accurately formed by placing a piece of circular sheet metal in a die and deforming the central part of the disk gradually to draw out the enclosure portion 63. A series of dies and drawing steps is usually necessary for proper formation of the enclosure portion of the shell assembly. Alternately, the shell assembly may be fabricated from a circular disk by cutting out an accurately located central hole, brazing the enclosure portion 63, already formed, around the edge of the hole and later bending the periphery of the disk downward to form the rim 62. An output coupling means 65 is provided at the end of the enclosure portion 63 of the shell subassembly 22 and includes a sleeve 66 inserted within an aperture in the enclosure portion 63 of the outer shell assembly and secured thereto. The output coupling means further includes a thin-bored tube 67 coaxial with tube 66 and hermetically sealed thereto, as by a glass bead 68. The shell sub-assembly 22 next is positioned over the assembly, shown in FIG. 4, made up of the anode subassembly 18 and the header subassembly 20, with the anode output coupling lead 34 inserted through the bore of tube 67 in the shell subassembly 22 and with the rim 62 of the shell subassembly engaging the rim 44 of the header subassembly 20. The sleeve 66 of output coupling means 65 is adapted to fit inside ring 33 0f the anode subassembly 18, so that there is capacitive coupling between the coaxial line including output coupling lead 34 and ring 33 and the coaxial line made up of output sleeve 66 and tube 67. The R.F. output lead 34 is sealed hermetically to the hollow tube 67 and the rings of the two nested cup-shaped members 42 and 6B of the respective subassemblies 20 and 22 are sealed in a vacuum-tight manner, as by welding or brazing.

The magnetron 10 then is exhausted by attaching a vacuum pump to the exhaust tube 49. After exhausting the tube, the exhaust tube 49 is pinched closed. Flexible leads 69, shown in FIG. 5, are attached to the lead-in wires 47 and 48 and the entire input side of the magnetron, including the exhaust tube 49 and the input lead-in subassembly 21 is encapsulated with a plug 71 made of an electrically insulating compound, such as rubber or plastic, to protect these parts from breakage during handling of the tube. The plug 71 may be formed by placing a cylindrical shell against the lower side of member 42 of the header subassembly 20 and inserting the encapsulating material into the shell under pressure. The shell is then removed after the plug has been fully formed.

It will be noted that the axis of symmetry of the anode block 24, indicated by the dashed line in FIG. 2,

that is an .axis passing through the center of the cathode space of the magnetron anode block 24 perpendicular to the face 54, is substantially perpendicular to the longitudinal axis of the magnetron tube assembly 12 which is indicated by the dashed line 92 in FIG. 2.

It is now necessary to mount the tube assembly 12 in the vicinity of a magnet assembly for providing a magnetic field transverse to the interaction space between the cathode and the" tips of the anode vanes. In one embodiment, the magnet structure is secured, as With glue, to an output transmission line in the form of a wave guide 75 having a closure plate 77 at one end and an open end leading to a load. A coupling hole is provided in the wave guide 75 through which the tube 67 of the output coupling means. 65 of the magnetron tube assembly 12 may. be inserted. A pair of threaded mounting posts 78 are secured fixedly to the wave guide 75, as by brazing at 79. The magnet is positioned along the Wave guide 75 so that the center of the pole pieces 81 and 82 of the magnet assembly 14 coincides with the 1 axis of symmetry 90 of the anode block 24 of the tube assembly 12. This position of the magnet assembly, in turn, is such that the distance of the magnetron output coupling probe 67 from the shorted end of the wave guide 75 provides for maximum transfer of energy from the magnetron tube to a load. The center line of the pole pieces of the magnet assembly 14 and that of the output coupling probe 67 of the magnetron tube 12 is approximately an odd multiple of quarter wavelengths distant from the closure plate 77 of the Wave guide, at

the operating frequency of the magnetron. The correct I position of the magnet and tube assembly with respect to the wave guide closure, however, is determined empirically for optimum coupling to the load. The space between the magnet pole pieces 81 and 82 is just sufficient to permit insertion of the enclosure portion 63 of the shell subassembly 22 of the magnetron tube assembly 12; and magnet assembly 14 thus serves as a guide for insertion of the tube assembly 12.

In order to hold the tube 12 fixed, a clamp ring 80, having a central aperture surrounding the encapsulating plug 71 and two mounting holes aligned with the mounting posts 78, is inserted in position over the sealed edges of the rims 44 and 62 of the tube assembly 12. A part of the base portion 61 of the shell element 60 of the shell subassembly, into which the member 42 of the header subassembly 20 nests, rests against one face 82 of the magnet assembly 14. Wing nuts 81 may be screwed onto the threaded mounting posts 78 to clamp the tube assembly 12 firmly against the magnet assembly 14.

Alternately, the portion 61 of shell element 60 may be sealed, as with glue, directly to the face 82 of magnet assembly 14, in which case the mounting posts 78, clamp ring 89, and wing nuts 81, may be dispensed with.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is: e y

.1. A magnetron comprising a cathode, a heater for said cathode, a header assembly including a member to which is attached an input sleeve for receiving cathode and heater lead-in conductors, and an anode surrounding said cathode and having a plurality of anode mem- 'bers at least partially defining cavity resonators, the portion of said cathode and heater lead-in conductors juxtaposed to said anode being positioned in alignment with first and second anode members respectively, said first and second anode members conducting high frequency currents which are in the same instantaneous phase.

;2. A magnetron comprising a cathode, a heater for said cathode, a header assembly including a member to which is attached an input sleeve for receiving cathode 6 and heater lead-in conductors, and an anode assembly including an anode block having a pair of opposite end faces, said anode block surrounding said cathode and having a plurality of anode members adjacent ones of which at least partially define cavity resonators, said anode block being mounted edge-wise on said member, said cathode and heater lead-in conductors being positioned in alignment with diiferent anode members which conduct high frequency current in the same phase and extending from said cathode and heater respectively in a plane parallel to one end face of said anode block.

3. A magnetron comprising a cathode, a heater for said cathode, a header assembly including a member to which is attached an input sleeve for receiving cathode and heater lead-in conductors, and an anode assembly including an anode block having a pair of opposite end faces, said anode block surrounding said cathode and having a plurality of anode members adjacentones of which at least partially define cavity resonators, said anode block being mounted edge-wise on said member, said cathode and heater lead-in conductors being positioned in alignment with different anode members which conduct high frequency current in the same phase and extending from said cathode and heater respectively in a plane parallel to one end face of said anode block, said leadin conductors each lying over and in alignment with anode members which conduct high frequency currents of like instantaneous phase.

4. A magnetron comprising a cathode-heater assembly containing a cathode and a heater for said cathode, a header assembly including a member to which is attached an input sleeve for receiving cathode and heater lead-in conductors, an anode assembly including an anode block having a pair of opposite end faces, said anode block surrounding said cathode, said anode 'block being mounted edge-wise on said member, said cathode and heater lead-in conductors being positioned in alignment with different anode members which conduct high frequency current in the same phase and extending from said cathode and heater in a plane parallel to one end face of said anode block, a ferrule of electrical insulating material surrounding at least one ofsaid lead-in conductors, and a clamp surrounding said ferrule and attached to said one end face of said anode block for supporting said cathode-heater assembly.

5. A magnetron comprising an anode block of uniform thickness with a substantially circular opening through the broadest face thereof, a plurality of anode members disposed radially within said opening and attached to said block forming cavities within said opening, a cathode disposed within said opening and coaxial therewith, a cathode heater disposed within said cathode and cathode and heater leads positioned in alignment with different. anode members which conduct high frequency currents in the same phase.

6. A magnetron comprising an anode block of uni form thickness with a substantially circular opening throughv the broad face thereof, a plurality of anode members disposed radially within said opening and attached to said block forming cavities within said opening, a cylindrical cathode disposed within said opening coaxial therewith, a cathode heater disposed within said cathode and cathode and heater leads contiguous with said broad face and in aligrnnent with different anode members which conduct high frequency currents in the same phase.

'7. A magnetron comprising an anode block of uni-form thickness with a substantially circular opening through the broad face thereof, a plurality of anode members disposed radially within said opening and attached to said block forming cavities within said opening, a cylindrical cathode disposed entirely Within said opening coaxial therewith, a cathode heater disposed entirely within said cathode and cathode and heater leads both contiguous with the same broad face of said anode block and in 7 alignment with difiFerent anode members which conduct high frequency currents in the same phase.

8. A magnetron assembly comprising; a header including a base portion and rim portion, said base portion being centrally apertured to permit passage of the magnetron cathode and heater leads; an anode shell including a base and rim portion dimensioned to snugly enclose said header base and rim portions and an anode enclosure attached to said anode shell base with its major dimension perpendicular to the major dimension of said anode shell base, said anode enclosure enclosing said magnetron anode and cathode which are arranged concentrically on an axis parallel to said major dimension of said anode shell base.

References Cited in the file of this patent 'UNITED STATES PATENTS 2,408,239 Spencer Sept. 24, 1946 2,458,142 Brown Jan. 4, 1949 2,475,960 Hegbar July 12, 1949 2,624,865 Nichols Ian. 6, 1953 2,765,425 Millman Oct. 2, 1956 2,824,261 Peters Feb. 18, 1958 

